Plaque Formation with ECHO Virus Types 15 to 24

Abstract

Summary ECHO virus types 15 through 20 and types 22 through 24 were studied in Rhesus renal epithelial monolayers for plaque production and for morphology of the plaques formed. All the types studied produced plaques by the fifth day after virus seeding, and three different plaque patterns were observed. Small, irregular plaques with diffuse boundaries and hazy centers were formed by ECHO virus types 15 through 20 and by types 22 and 23; on the basis of plaque morphology, they apparently belong to the “Group A” of Melnick (11). ECHO type 19 also formed another type of plaque which was large, irregular, with diffuse boundaries and clear centers. This did not easily fit into either Group A or Group B. The third pattern was produced by ECHO virus type 24, and was samll, irregular, with sharp boundaries and clear centers; it might form a subgroup with types 1 and 13, and apparently belongs in Group A. To date, four distinct plaque patterns have been observed to be produced by ECHO viruses, and grouping of ECHO viruses according to plaque morphology should aid in their study.